KEF Q900 Recommended Amplifier

The Q900 is 91db sensitive and is rated at 8ohm.

How large is your room?
How far away are you sitting from the speakers?
How loud are you wanting to play these (reference level)?

Depending on the above a pre-pro may be unnecessary, unless you have a very large room or are really going to drive these hard.

Decent preamps are going to cost from $1000 to $5000, so maybe you want to go with an integrated amplifier.

The best-sounding integrated amplifer I know of for under $1000 is the Music Hall 15.2, which was $800, but Music Direct is selling it right now for only $499. That is a steal at that price, and would work well with those speakers.

A step up from that would be the Musical Fidelity M3i, but it is $1500. I recommend it very highly for those speakers.

The Cambridge amplifiers are not bad, but the two I mentioned are definitely better-sounding.

Either one of those will drive the Q900 just fine; it has very good sensitivity. Any integrated amplifier from 60 watts up will be quite adequate.

If you had $2000 to spend, the Vincent SA31 preamp and SP331 power amplifier will run about that much and be another major step up.




Edited by commsysman - 7/17/12 at 9:36am

The Musical Fidelity M3i for $1500.

no point to bi-wire.

This seems like overkill. Why not just start with a standard receiver like a Denon, Pioneer Elite, Onkyo, Marantz, etc and determine if you need more. Again, you are buying an efficient speaker that is sitting in medium to small size space. It won't take much to drive these. If it was me, I would save on the receiver and put the money towards something else.

Yes, you certainly can, but I would see no reason to.

An amplifier like the Musical Fidelity M3i has a lot of money invested in the parts quality and hi-current power supply design of the AMPLIFIER, while almost all HT receivers have inadequate power supplies and about $20 per channel invested in the amplifers. 90% of the engineering and money put into an HT receiver goes into features that have nothing to do with decent sound quality or adequate power supply size, and the result is predictable; poor sound quality.

HT receiver designs are driven by the sales department; they want a long long list of gee-whiz signal-processing and video-processing features to put in the sales brochure /spec sheet, and could care less how it sounds.

Their sound quality is not very good at lower levels and deteriorates badly when they are driven hard at all.

Connecting an HT receiver to a pair of Q900 speakers would be like trying to tow a 35-foot travel trailer with a Toyota Corolla; insane! It's not designed for it.

The M3i amplifier has excellent sound quality and the kind of current capability needed to drive a large 4-ohm speaker like the Q900 on peaks with no distortion.




quote name="ack_bk" url="/t/1420623/kef-q900-recommended-amplifier#post_22226511"]
This seems like overkill. Why not just start with a standard receiver like a Denon, Pioneer Elite, Onkyo, Marantz, etc and determine if you need more. Again, you are buying an efficient speaker that is sitting in medium to small size space. It won't take much to drive these. If it was me, I would save on the receiver and put the money towards something else.[/quote]
Edited by commsysman - 7/17/12 at 10:58am

[/quote]

Can you please provide measurements showing the deterioration of sound for these speakers when being played at reference level with a 2 channel Denon, Marantz, etc receiver? Please demonstrate, scientifically, how these other amplifiers are so superior when driving an efficient 8ohm speaker. Surely you have the measurements to backup these claims.

As already stated, the Q900 is 8ohm , not 4ohm.

http://www.kef.com/html/en/showroom/hi-fi_series/q_series/fact_sheets/Floorstanding/Q900/

If you take the trouble to read the 2011 review of the Q900 in Stereophile, you will see extensive laboratory test results that, IF you are the least bit knowledgeable, will convince you that the Q900 is without question a 4 ohm speaker and needs to be driven by an amplifier much more robust than those normally found in HT receivers.

The measured impedance of the speaker is 4.1 ohms at 60 Hz, 3.6 ohms at 160 Hz, and 4.0 ohms at 9 Khz. Anyone who characterizes that speaker as an 8 ohm speaker is seriously ignorant of the facts. Its actual measured impedance curve clearly shows that it is a load of 4 ohms or less throughout its operating range, and needs to be treated as a 4 ohm speaker when selecting an amplifier to drive it.

I find it rather ridiculous that you make such wildly incorrect claims when careful reading of that one article would inform you of your lack of knowledge of the basic facts.

Kindly don't demand that I prove anything to you until you make a good-faith effort to learn the basic facts of the matter; I am not your servant or your assistant. READ the whole article, please, and then there may be some basis for discussion when you have some facts in hand.




Can you please provide measurements showing the deterioration of sound for these speakers when being played at reference level with a 2 channel Denon, Marantz, etc receiver? Please demonstrate, scientifically, how these other amplifiers are so superior when driving an efficient 8ohm speaker. Surely you have the measurements to backup these claims.
As already stated, the Q900 is 8ohm , not 4ohm.
http://www.kef.com/html/en/showroom/hi-fi_series/q_series/fact_sheets/Floorstanding/Q900/[/quote]
Edited by commsysman - 7/17/12 at 11:35am

Before you do anything else, you should read the Stereophile review of the Q900, which is available online. It is definitely a 4 ohm speaker, regardless of what KEF rates it at. Look at the frequency vs impedance graph and then you will know the truth. Its impedance drops as low as 3.6 ohms.

[/quote]

Well, then blame the manufacturer, they rate it as 8ohm. You do realize that Marantz, Denon, Onkyo, etc all make 2 channel receivers that are rated for 4ohm.

I have seen salesmen push the need to buy expensive amps (in this case you are recommending $1500 amp to drive a $1500 pair of speakers) to drive efficient speakers before and, from my own personal experience, listening to efficient speakers at moderate levels (with peaks near reference) I could not tell the difference between a $2000 amp and a $500 amp. Several of us have done a blind A/B comparison with a Denon 3000 series receiver and an XPA-5 Emotiva amp and none of us could point out which amp was driving the speakers. There was no noticeable difference in sound.

There are many factors to consider like the size of the room, seating distance to the speaker, etc. Even the MSI amp you are recommending is only rated at 76 watts?

My advice to the OP is this. Buy a good $500 or so 2 channel amp that is rated 4ohm and buy a more expensive amp like the one recommended above locally from a store with a good return policy. Compare the two in your room with your speakers and your own ears. Keep the one you find to be superior and be happy.

So?  Speakers have impedances that vary widely with frequency so that, if one wants to use one number, one can choose the measurement at any frequency and be correct.  However, if you look at the measured impedance curve, it hits 8ohms several times in passing from lower values to higher peaks but it is in the 4ohm range for most of the range, especially in the bass.  JA writes: "The speaker's impedance is specified as 8 ohms, but as fig.1 shows, the impedance drops to 4 ohms in the top octaves and to below 4 ohms in the lower midrange, reaching a minimum value of 3.17 ohms at 160Hz. There is also a combination of 5 ohms magnitude and –42° electrical phase angle at 80Hz, meaning that the KEF does need to be used with a good 4 ohm–rated amplifier or receiver."

 

Kal

For most average size rooms (like 18' x 20') and volume of no more than 95dB from 12ft away, a Denon 3312 would be more than enough. You can call Electronics Expo and see if they would sell for $550 - tell them Amazon had a $550 shipped deal few weeks ago, but you missed the sale.

You can always add an amp later, which usually never hurts, but I doubt if you even need it. The Denon 3312 can output 225 wpc x 2ch into 4ohm.

Actually I think any good 100wpc AVR will do. But if you can get the 3312 for $550, why not?
Edited by AcuDefTechGuy - 7/17/12 at 6:46pm

So I continue to see people say they compared an XPA-3 or XPA-5 to a receiver and couldn't hear the difference and then conclude that all amps sound the same. I have not heard anyone say they compared a upper end Krell or other renouned solid state amp to a receiver and say they sounded the same. For that matter I have not heard that with the XPA-2 or XPA-1 either. I have heard the UPA-1s and preferred the receiver so I am not surprised on the XPA-3&5. I wish I could have heard the XPA-1s, guessing they might be very special and am very intrigued by their new class H Reference line. I am still in the camp that believes amps can matter and recent experiences have further solidified that belief.

Nobody is saying amps don't matter. You would not want to drive inefficient 4ohm speakers with a low wattage amp rated for 8 ohm speakers.

I have yet to see anyone prove, scientifically,that similar rated (power) amps that are level matched have a drastic difference in sound quality because one costs $2k and one costs $6k....

Mark Levinson is upper high-end. ATI makes some amps for Mark Levinson. I can hear a very, very significant difference between my Denon AVR and the ATI amps - the ATI amps are a lot LOUDER.

Probably because the ATI amps have a 34dB gain. Just like how many amps have a 32-34dB gain.

But once I increase the speaker channel levels on the AVR to match the ATI amp, I cannot hear one bit of difference.

And of course, there's that infamous $300 Pioneer AVR vs $10,000 Boulder amp double-blinded study where audiophiles could not significantly even tell the difference.

For 2 channel music in your room - this Harman Kardon would be a good one,
and save you some money > I would test this out, and it can handle 4ohms.
http://www.amazon.com/Harman-Kardon-HK-3490-Receiver/dp/B00198F89A/ref=sr_1_1?ie=UTF8&qid=1342581573&sr=8-1&keywords=harmon+kardon+hk3490

Measurements and review here
http://www.audioholics.com/reviews/receivers/hk-3490/hk-3490-measurements
http://www.audioholics.com/reviews/receivers/hk-3490

"Into 4-ohm loads, the HK 3490 exceeded its 150wpc power rating by putting out 167wpc x 2 @ 0.1% THD
+ N and a whopping 227wpc of dynamic power with both channels driven"
Edited by zieglj01 - 7/17/12 at 8:44pm

Well, I would definitely want an amp or AVR that can do 4ohms easily. The Denon 3312 (which has been as low as $550) can output 225wpc x 2ch 4ohms. That is more than enough.

note that this HK amp is frequently on sale on amazon for like 270-300. it's currently 450 so I'd hold off for a bit for it to drop.

This info just REALLY bummed me out. I was planning on buying a pair of KEF Q900 towers and matching Q600 center. However my amp is a Pioneer Elite SC-25 and is NOT recommended to drive any speaker at 4 ohm.

Ughh, the search continues.

It should be able to drive a pair of Gallo Acoustics CL-3 speakers, which IMO are better speakers.

Check out the article on them (from The Absolute Sound).

60-day free trial when you order from Gallo direct.

You can certainly use that receiver to drive TWO or THREE low-impedance speakers, or FIVE 6-ohm speakers, but if you are going to be running 7.1, then you better stick to 8-ohm speakers.

It is the total current available from the power supply that is the issue.
Edited by commsysman - 1/31/13 at 3:07pm

No such recommendation actually exists.

It is true that the official power ratings are only given at 6 and 8 ohms, but this is because of the legal requirement for power ratings to be based on tests involving pure tones and resistive loads.

Music has far less energy in it than a pure tone of the same amplitude.

The difference is no less than 3, and can be 10 or more. IOW music with instantaneous peaks of 100 watts can contain the same average power as a pure sine wave of from 5 to 30 watts.

For example here is a musical selection I picked randomly:



Here are its statistics:




Here is a pure sine wave:



Here are its statistics:



Notice that there is an approximate 10 dB or more difference in the average power contained in the sine wave as there is in the music. The sine wave has about 10 times as much average power as music with about the same peak amplitude.

Speakers are a load whose impedance varies with frequency and is often higher than its rating which is usually taken at a minimum or near-minimum.

This is especially true of the Q900s whose impedance curve looks like this:



The speaker's actual impedance is 6 ohms or more over almost half of the audio range.

There will be no problems.
Edited by arnyk - 1/31/13 at 3:19pm

Thank you! That is a relief.

Would you be opposed to going with a preamp and amp rather than an integrated? A Parasound 2100 preamp paired with an amp of your choice would make a killer combo for your price range of $1700. If you don't already have a receiver or aren't opposed to using one for music listening, the Denon 4311 would be an awesome choice as well.

The "all amps sound the same when level matched and used within their rated means" debate always touches a nerve with people. Instead of giving my opinion on it I will instead say this: get a good amp to ensure your speakers have ample power, especially during dynamic movie and music passages. Transients don't occur often or for very long, but they can cause your amplifier to clip if it isn't up to snuff. Get the best amp you can, because it certainly won't hurt anything. Whether you "hear" a difference is for you to decide. Some people swear they do, while others say you won't. Whichever you camp you fall into, go with whichever makes you happy. That's all that matters.